ATMOSPHERE AEROMICROFLORA AND DISPERSAL OF MICROBES The kind

• ATMOSPHERE: AEROMICROFLORA AND DISPERSAL OF MICROBES

• The kind and number of airborne microbes vary tremendously in different environments and dependent upon the activity in the environment and upon the amount of dust stirred up. The most significant environmental factors influencing viability of microbes are temperature, relative humidity and wind velocity. Other factors influencing their survival are oxygen, air ions, solar irradiance and open air factors. Among the microbes present in the atmosphere, bacteria are highest in number. In Outdoor air.

• Soil organisms predominate. Indoors, the numbers of microbes are considerably higher than that in the outdoors, especially those originating in the human respiratory tract. Molds and yeasts are numerous in some area also out number the bacteria. Aspergillus, Penicillium, Acremonium, Fusarium, Nigrospora, Zygosporium, Aureobasidium, Pithomyces, Mucor and Rhizopus. •

• Bacteria have no active mechanisms for becoming airborne. They are dispersed on dust particles disturbed by physical agencies etc. Bacteria commonly found in air include both aerobic sporeformers (eg. Bacillus) and non spore formers, eg. Micrococcus and Sarcina. The most dominant bacterium is Bacillus Subtilis commonly called hay Bacillus, they reside in soil and decaying vegetation. Marine air also contains microbes although to a lesser extent than terrestrial air. Bacterial genera such as Achromobacter, Bacillus, Corynebacterium, Flavobacterium, Micrococcus, Sarcina and Staphyloccus these are often found in marine air.

Airborne Microorganisms • • Bacteria comprise a heterogeneous group varying in size from 0. 3 to 10 -12 m and those bacteria that are capable of with standing prolonged desiccation only can persist in air for long periods. Such forms are saprophytic. Among these are sporulating species of bacilli, Cocci like Sarcina and non-sporulating rods like Serratia. However it is common to find throat and mouth inhabiting bacteria exemplified by Streptococcus, Staphylococcus, Pneumococcus etc. in air.

• Protozoa- Most of the protozoan’s are transported as cysts: the Cysts range from 2 -50 um in diameter. • • Microalgae- Some common airborne microalgae are chlamydomonas, Chlorococcum, Phormidium, Protococcus, Diatoms, Spirogyra, Oscillatoria, Chlorella, Amphora. Some cyanobacteria like Aulosira, Lyngbya, Nostoc are also found in air. • Hyphal fragments of microfungi constitute a significant population of air spora, these are primarily the Conidiophores of asexual forms. They mostly belong to Cladosporium, Alternaria and Penicillium. • • •

Outdoor and indoor microflora: • • Outdoors, fungal spores are almost always present in air but their number and types vary depend on the time of day, weather, season and geographical location. In outdoor air, soil Organisms dominate. Indoors microbes are higher in number than outdoors, especially for those originating with respiratory tract. Indoor aerospora is also variable, with dominance of Aspergillus and Penicillium.

Night fungal flora • • Fungal spora varies considerably during the day and night time. Spores with active mechanisms requiring water are usually most numerous in the air at night, following dew formation or rain. Ascospores, basidiospores and ballistospores of sporobolomyces and related mirror yeasts increase in numbers during night. • •